@moderna_tx mRNA vaccine is finally arriving in Australia. It is very similar to the @BioNTech_Group / @pfizer #mRNA The main difference is in the lipid nanoparticle (LNP) that deliver the mRNA. This is both in terms of the lipid chemistry and how the LNP's are formed 1/10

Both companies use a mixture of 4 lipids/PEG-lipids in their LNP formulations. The most important of those is the lipid that binds to the mRNA during the LNP formulation. These are the so-called ionisable lipids. Why? Because at certain pH levels they are positively charged 2/10

So at a fairly low pH, they are positively charged and bind strongly to the mRNA. This is how the two form a nanoparticle. The other 3 lipids/PEG-lipids (see the ones for the Pfizer below) are "helper" lipids, each playing different role in forming the LNP and making it work 3/10

Once the LNP is formed the pH is raised to neutrality, and the lipids are no longer positively charged. After vaccination, the LNP then gets into your cells and into the acidic endosomes, where the pH drop again charges these lipids which now helps releasing the mRNA. 4/10

But is that all then in terms of the differences between the "Pfizer" and Moderna LNPs? We think not! A key research area for the @UNSWRNA is RNA delivery systems and based on our own experience it is not just what you use to form a LNP but HOW they are made that matters! 5/10